Wireless charging systems allow powering and charging of portable devices by using energy from electrical or magnetic fields in proximity to the portable devices instead of providing power via a wired connection. Wireless charging may be used in various applications including electric tooth brushes, mobile phones, televisions, cars, etc. In these applications, typically a single transmitter is used to charge a single receiver. Such a one-to-one relationship may be imposed due to limitations of magnetic induction (MI) technology. For example, a multi-device charging mat that uses MI technology includes several transmitters to support several receivers of devices that are placed on the mat, so that a one-to-one relationship between transmitters and receivers is maintained. Wireless charging using magnetic resonance (MR) technology enables multiple receiver devices positioned in proximity to the transmitter to be charged simultaneously.